Topic Contents

Uric Acid in Urine

Test Overview

The uric acid urine test measures the amount
of
uric acid in a sample of urine collected over 24
hours. Uric acid is produced from the natural breakdown of your body's cells
and from the foods you eat.

Most of the uric acid is removed from
the body in urine. A small amount passes out of the body in stool. But if too
much uric acid is being produced, the level in the urine will increase. If the
kidneys are not able to remove it from the blood normally, the level of uric
acid in the urine will decrease.

High blood levels of uric acid in
the body can cause solid crystals to form within joints. This causes a painful
condition called
gout. If gout remains untreated, uric acid crystals
can build up in the joints and nearby tissues, forming hard lumpy deposits
called
tophi. High levels of uric acid in the urine can cause
kidney stones.

Why It Is Done

A uric acid urine test is done
to:

Check to see if kidney stones may be caused by
high uric acid levels in the body.

Find the cause of a high level
of uric acid in the blood and help choose the proper treatment.

How To Prepare

No special preparation is required
before having a uric acid urine test. It is not necessary to restrict fluids or
foods before the test. Be sure to drink enough fluids during the 24-hour urine
test to prevent
dehydration.

During the collection
period, do not drink alcohol, because alcohol reduces the amount of uric acid
eliminated by the kidneys.

Many medicines can change the results
of this test. Be sure to tell your doctor about all the nonprescription and
prescription medicines you take.

Talk to your doctor about any
concerns you have regarding the need for the test, its risks, how it will be
done, or what the results may mean. To help you understand the importance
of this test, fill out the
medical test information form(What is a PDF document?).

How It Is Done

A uric acid urine test is usually done
on a sample taken from all the urine produced in a 24-hour period.

To collect your urine for 24 hours:

You start collecting your urine in the morning.
When you first get up, empty your bladder but do not save this urine. Write
down the time that you urinated to mark the beginning of your 24-hour
collection period.

For the next 24 hours, collect all your urine.
Your doctor's office or lab will usually provide you with a large container
that holds about 1 gal (4 L).
The container has a small amount of preservative in it. Urinate into a small,
clean container and then pour the urine into the large container. Do not touch
the inside of the container with your fingers.

Keep the large
container in the refrigerator for the 24 hours.

Empty your bladder
for the final time at or just before the end of the 24-hour period. Add this
urine to the large container and record the time.

Do not get toilet
paper, pubic hair, stool (feces), menstrual blood, or other foreign matter in
the urine sample.

How It Feels

There is no pain while collecting a
24-hour urine sample.

Risks

There is no chance for problems while collecting
a 24-hour urine sample.

Results

The uric acid urine test measures the
amount of
uric acid in a sample of urine collected over 24
hours.

The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.

Some medicines, such as allopurinol,
insulin, some diuretics, and high levels of aspirin.

Drinking
alcohol during the collection period.

What To Think About

Having a high uric acid level does not mean
that you have
gout. If your uric acid level is high and you do not
have any other symptoms, you will not need to take any medicine to decrease
your uric acid level.

If you have kidney disease or have had a
problem with kidney stones, your doctor may start treatment with a medicine,
such as allopurinol, even if your uric acid levels are not too
high.

About 10 out of 100 kidney
stones are made of uric acid. These white or orange stones are hard to see
on an abdominal X-ray. Uric acid stones can form when urine has a low
pH (is very acidic). People who have gout are at high
risk of developing uric acid kidney stones. Allopurinol (such as Zyloprim) may be prescribed without doing a 24-hour uric acid urine level
test if a person has significantly impaired kidney function or
tophi. Tophi are chalky, white accumulations of uric
acid crystals that build up in the soft tissue of a joint, often occurring in
the joints of fingers. Tophi may also develop in the cartilage of the external
ear, the back of the fingers, or the elbow.

The chance of having
high levels of uric acid in the urine increases under some conditions, such as
from receiving
chemotherapy for some types of cancer.

If the urine uric acid is greater than 750 mg per 24-hour urine
sample, a person with gout is usually treated with a medicine such as
allopurinol that decreases the body's
production of uric acid. A person in this situation is called an
"overproducer."

If the urine uric acid is less than 750 mg per
24-hour urine sample, a person with gout may be treated with a medicine such
as probenecid (for example, Probalan) that increases uric acid elimination by
the kidneys. A person in this situation is called an
"underexcretor."

A person with tophi or uric acid kidney stones
will be treated for high uric acid levels no matter what the results of the
uric acid test are.

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